Topeak Alien LUX Bike Taillight (Yellow) Lamp: 2 Red LED?s Battery: CR2032 (2) (Included) Control: 2 Modes. Constant/Blinking , Mount: Seatpost, Topeak Bags Size (L x W x H): 1.9 x 1.4 x 1.2 inches Weight: 20.6 g / 0.73 oz